Dellorto DHLA 40 - Pump jet ball bearing - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 8 (permalink) Old 08-30-2015, 10:22 AM Thread Starter
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Dellorto DHLA 40 - Pump jet ball bearing

Hello!

I'm new here and I am partly restoring my 2000 GTV Bertone from 1974.

After I overhauled my Dellorto Carbs, I noticed a whistling noise - After that I saw that the Pump jet ball bearing was stuck in the carburetor case.

After I got it out i dried the carburetor case very well and I re-installed the ball, but it was still stuck. I didn't notice any damage on the carburetor case - it's in pretty good shape.

By the way I am referring to part no 51 on the diagram: http://www.gruntled.com/Dellorto/Diagram.html

Has anyone experienced a similar problem? It would be a shame to have to buy a new carburetor because of this.

Thanks in advance and regards from Switzerland,
Che
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post #2 of 8 (permalink) Old 08-30-2015, 04:24 PM
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Are you sure the whistling noise is not originating from the starter circuit? These trend to make a lot of noise

Spider 2.0i 1992 | GTV 2000 1971 | Giulia Spider 1963
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post #3 of 8 (permalink) Old 08-30-2015, 09:26 PM Thread Starter
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Hi Rafael, thanks for your reply

I can't exclude that the noise is coming from somewhere else than the carbs but it's the only mechanical parts i changed so far. And the noise let me to realize that the ball bearing was stuck in the carburetor case.
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post #4 of 8 (permalink) Old 08-31-2015, 03:19 PM
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Sorry, my post was not clear.

Dellortos have a starter circuit, also called the choke. When enabled this circuit makes lots of noise. The choke or starter is enabled by the starter cable. Disconnect the starter cable from both carbs to make sure that the starter circuit is disabled.

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post #5 of 8 (permalink) Old 09-01-2015, 10:59 PM
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Che, your last diagram is from a Weber, not Dellorto
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post #6 of 8 (permalink) Old 09-03-2015, 12:08 AM Thread Starter
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@rafael

Thank you, I will try it on the weekend.

@quadrifoglio

You are right of course, I just wanted to illustrate the ball bearing in the context of a diagram.


In the meantime, I was able to get my hands on a pair of Dellorto DHLA 40's, so I can replace my old ones. I want to make sure, as the ball bearing regulates the pump delivery valve.

The question remains, how a stuck ball bearing can be fixed. Or let me put it else: If the ball bearing is stuck, should the carb be replaced? I ultrasonic-cleaned the carb twice and the ball bearing was still stuck, so I have to assume that the inner case of the carb has suffered some damage.

Anyway, thanks for the input so far.

'74 2000 GT Veloce

Last edited by Che; 09-03-2015 at 12:11 AM.
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post #7 of 8 (permalink) Old 09-03-2015, 02:15 PM
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I do not understand how a stuck ball can make such a noise. If the engine is revving at constant speed, then the accelerator pump is not used.

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post #8 of 8 (permalink) Old 09-14-2015, 02:51 AM Thread Starter
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For the sake of completeness: The sound was definitely not caused by any damage to the carbs. I exchanged my Dellortos 40s with revised ones. It was then that we found out that the sound was coming from a faulty rubber flange. The damage must have come from the unmounting.

Che

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